The project is focused on the elucidation of molecular mechanisms that operate during immune activation. In particular we have studied the genetic response of mitogenically activated T cells. Previously we have cloned many novel immediate-early induced genes of T cells. These genes encode for various transcription factors, including NF-kappaB, various cytokines, receptors and a number of intracellular signal-transducing components. We have now extended these studies to clone as yet undiscovered genes which are induced later during the cascade of events which ultimately lead to proliferation and full differentiation of the stimulated T cells. Activation of NF-kappaB is critical for immune function of stimulated T cells, since this factor regulates the expression of many immunomodulatory gene products; in addition, it regulates several viruses, including HIV. NF-kappaB also plays an important role during the virus transformation and activation of T cells by the HTLV I virus encoded Tax protein. We have discovered that Tax activates NF-kappaB by at least two mechanisms. The primary mechanism involves Tax-mediated degradation of the IkappaB-alpha inhibitory protein, the main cytoplasmic inhibitor of NF-kappaB. Tax causes the proteolytic degradation by inducing site-specific phosphorylation of the IkappaB-alpha inhibitor. We are studying the membrane-proximal events which occur during stimulation of immune cells with TNF-alpha, a potent activator of NF-kappaB. We have cloned as an immediate-early gene of T cells a member of a novel family of signal-transducing proteins which associate with the TNF receptor family. In addition, we are investigating the signaling path which leads from the T cell receptor to activation of NF-kappaB.